A little more than two months after the national blood agency called on Canadians to respond to its “critical” need for donations, the national supply is once again slipping.

In June, when Canada’s blood supply dipped below 12,000 units, donors lined up to restore it to a 23,000-unit peak (Canadian Blood Services says it needs 20,000-25,000 units in its inventory to adequately serve hospitals across the country).

But slowly, it has begun to fall and agency officials worry it could soon return to a critical state. By August’s civic holiday, inventory had already fallen back to nearly 18,000 units.

The problem is chronic, part of an ongoing trend the agency struggles with.

It is led in large part by the reluctance of many Canadians to book return appointments. As a result, supply continues to return to dangerous levels, according to Michael Betel, CBS director of donor relations.

“The response across the country was truly incredible. But what happens is when we have critical need messaging, donors respond and when the urgency drops, so do collections,” he said. “We’re constantly working to try to impress upon people the need to continue to give. That need for blood is constant and every single day patients need blood products.”

In part, the agency’s collection challenges are also self-inflicted.

In the last year, the agency moved the time that women must wait between donations from 56 to 84 days to allow for proper recovery of iron levels, while also bumping required hemoglobin levels for male donors from 125 grams per litre to 130.

Men who have sex with men must still be abstinent for a year before they can donate, a waiting period that was reduced from five years in August of 2016 and from a lifetime deferral less than three years before that.

Many in the medical world and LGBTQ community have criticized the ongoing deferral.

Jane Greer, the director of Hassle Free Clinic, a longtime Toronto sexual health clinic, calls the ongoing deferral period for sexually active gay men “ridiculous.” She says even the most conservative science would put a waiting period at 12 weeks, to account for the longest potential window between HIV exposure and detection.

“There’s no, no basis for it. In the face of science, it just smacks of very old and very prejudicial notions about HIV and gay men,” she said. “Everybody knows that. I don’t even know what they’re thinking. I can say with absolute certainty that the policy is outdated, it’s stigmatizing, and it does not reflect the science we have available to us now.”

Dan Allman, the acting director of the University of Toronto’s HIV studies unit, said Canada’s 1980s HIV crisis left a complex legacy, one the country has struggled to divorce itself from. Thousands of Canadians were exposed to Hepatitis C and HIV through contaminated blood products leading to an expensive class action lawsuit.

“The blood scandal had an enormous impact and it’s quite a while ago now and a lot of people have a tendency to forget that and not remember the reasons for the blood deferral in the first place,” he said.

Nonetheless, Allman says Canada hasn’t caught up to the science and that anger among those who need donations and gay men who are excluded is rightly justified.

“I think that if one were simply going to rely on the HIV science, the science of detection, that it is pretty difficult to justify a long deferral period,” he added.

The Canadian Medical Association issued a policy statement last year urging “Canadian blood service providers and Health Canada to adjust eligibility for blood donors so that these criteria are behaviour-based and do not consider sexual orientation.”

Health Canada said its relationship with the blood agency, which calls itself an independent body, takes an arms-length approach.

Health Canada can only broadly mandate the CBS make changes when there’s an urgent safety issue, like the outbreak of the Zika virus, according to Catherine Parker, who runs the ministry’s biologics and genetic therapies directorate.

Otherwise, while Health Canada has final approval over all proposed changes to donor restrictions, they can only adjust CBS proposal if it is to add a greater buffer rather than reduce one.

Parker said Health Canada has made it clear to CBS that they’re open to further changes to the wait period for men who have sex with men but that there’s “nothing on the horizon right now.”

Last year, in its approval of the reduction of the deferral to one year, Health Canada wrote that the window period for HIV testing is now “less than 10 days.”

There have been “no cases of HIV transmission by blood transfusion in over 25 years in Canada,” it concluded.

“Our bar is that we have to be convinced that this change will not diminish safety and we were convinced when we reviewed it,” Parker said.

Betel says the blood agency understands the concerns many have with the current deferral period.

“It’s great that it has gone from unable to donate to five years to one year but for people that are involved and unable to donate, it’s frustrating for them and for them it feels like forever anyway and I totally get that and so does the organization,” he finished. “It’s one of those situations where we want more donations too.”

But action is still required.

“I think undoubtedly that a stigma existed before, that a stigma has been enfranchised if you will and it continues to be reproduced,” Allman said. “How will our children and grandchildren look back historically and think of how we approached the blood ban?”